Turbidity detection devices for detecting the turbidity of a liquid accommodated in a transparent container, which is the object of turbidity detection, are widely known (for example, refer to Japanese Laid-Open Patent Publication No. 5-133893). The turbidity detection device disclosed in Japanese Laid-Open Patent Publication No. 5-133893 transmits light from a light source through a transparent container and a photoreceptor receives the transmitted light, and the turbidity value of the material subjected to turbidity detection is obtained from the amount of received light. Since the amount of transmitted light passing through the transparent container decreases as the turbidity of the material subjected to turbidity detection increases, it is possible to obtain a turbidity value based on the amount of transmitted light.
In the conventional turbidity detection device mentioned above, however, the amount of light transmitted through the transparent container decreases in conjunction with the turbidity of the material subjected to turbidity detection and the scattered light increases therewith, and since some of the scattered light enters the light-receiving surface of the photoreceptor, the amount of received scattered light increases in conjunction with the increase in turbidity, and this increase generates errors in turbidity detection.
Furthermore, a lens is provided between the transparent container and the photoreceptor to prevent the generation of error, and although it is possible that this lens will prevent the scattered light from entering the photoreceptor, a problem of error generation arises due to the thermal deformation of the lens caused due to temperature when, for example, the turbidity detection device requires temperature management as in the case of nucleic acid detection devices.